I propose to use quantitative EM autoradiography together with standard neurobiological procedures to study molecular events at neuromuscular junctions (nmj) on the finestructural level. Initially the major emphasis will be to study the localization and quantitation of the various esterases and the acetylcholine receptor in normal, embryonic and diseased vertebrate muscle. Attempts will be made to study the relative role played by muscle and nerve (axon and Schwann cell) in their synthesis and turnover, the in vivo effect of their inactivation, and the sequence of events during recovery. We hope to obtain meaningful correlations between the molecular quantitation and function. The binding of the neuromuscular transmitters, glutamate and Gaba at invertebrate nmj's and their response to nerve stimulation will also be studied in an attempt to determine the mechanism of transmitter inactivation and reutilization at these junctions.